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Add internal curve checking, using BigInt
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@reardencode
reardencode committed Mar 22, 2022
1 parent a04b9d5 commit 1c44f41
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Showing 7 changed files with 122 additions and 100 deletions.
4 changes: 2 additions & 2 deletions src/payments/p2tr.js
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Original file line number Diff line number Diff line change
Expand Up @@ -196,7 +196,7 @@ function p2tr(a, opts) {
else pubkey = tweakedKey.x;
}
if (pubkey && pubkey.length) {
if (!_ecc().isXOnlyPoint(pubkey))
if (!(0, types_1.isXOnlyPoint)(pubkey))
throw new TypeError('Invalid pubkey for p2tr');
}
if (a.hash && a.scriptTree) {
Expand Down Expand Up @@ -251,7 +251,7 @@ function p2tr(a, opts) {
const internalPubkey = controlBlock.slice(1, 33);
if (a.internalPubkey && !a.internalPubkey.equals(internalPubkey))
throw new TypeError('Internal pubkey mismatch');
if (!_ecc().isXOnlyPoint(internalPubkey))
if (!(0, types_1.isXOnlyPoint)(internalPubkey))
throw new TypeError('Invalid internalPubkey for p2tr witness');
const leafVersion = controlBlock[0] & LEAF_VERSION_MASK;
const script = witness[witness.length - 2];
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31 changes: 0 additions & 31 deletions src/payments/verifyecc.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,37 +3,6 @@ Object.defineProperty(exports, '__esModule', { value: true });
exports.verifyEcc = void 0;
const h = hex => Buffer.from(hex, 'hex');
function verifyEcc(ecc) {
assert(typeof ecc.isXOnlyPoint === 'function');
assert(
ecc.isXOnlyPoint(
h('79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798'),
),
);
assert(
ecc.isXOnlyPoint(
h('fffffffffffffffffffffffffffffffffffffffffffffffffffffffeeffffc2e'),
),
);
assert(
ecc.isXOnlyPoint(
h('f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9'),
),
);
assert(
ecc.isXOnlyPoint(
h('0000000000000000000000000000000000000000000000000000000000000001'),
),
);
assert(
!ecc.isXOnlyPoint(
h('0000000000000000000000000000000000000000000000000000000000000000'),
),
);
assert(
!ecc.isXOnlyPoint(
h('fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f'),
),
);
assert(typeof ecc.xOnlyPointAddTweak === 'function');
tweakAddVectors.forEach(t => {
const r = ecc.xOnlyPointAddTweak(h(t.pubkey), h(t.tweak));
Expand Down
2 changes: 1 addition & 1 deletion src/types.d.ts
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
/// <reference types="node" />
export declare const typeforce: any;
export declare function isPoint(p: Buffer | number | undefined | null): boolean;
export declare function isXOnlyPoint(p: Buffer | number | undefined | null): boolean;
export declare function UInt31(value: number): boolean;
export declare function BIP32Path(value: string): boolean;
export declare namespace BIP32Path {
Expand All @@ -20,7 +21,6 @@ export interface Tapleaf {
}
export declare type Taptree = Array<[Tapleaf, Tapleaf] | Tapleaf>;
export interface TinySecp256k1Interface {
isXOnlyPoint(p: Uint8Array): boolean;
xOnlyPointAddTweak(p: Uint8Array, tweak: Uint8Array): XOnlyPointAddTweakResult | null;
privateAdd(d: Uint8Array, tweak: Uint8Array): Uint8Array | null;
privateNegate(d: Uint8Array): Uint8Array;
Expand Down
69 changes: 54 additions & 15 deletions src/types.js
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Original file line number Diff line number Diff line change
@@ -1,30 +1,69 @@
'use strict';
Object.defineProperty(exports, '__esModule', { value: true });
exports.oneOf = exports.Null = exports.BufferN = exports.Function = exports.UInt32 = exports.UInt8 = exports.tuple = exports.maybe = exports.Hex = exports.Buffer = exports.String = exports.Boolean = exports.Array = exports.Number = exports.Hash256bit = exports.Hash160bit = exports.Buffer256bit = exports.Network = exports.ECPoint = exports.Satoshi = exports.Signer = exports.BIP32Path = exports.UInt31 = exports.isPoint = exports.typeforce = void 0;
exports.oneOf = exports.Null = exports.BufferN = exports.Function = exports.UInt32 = exports.UInt8 = exports.tuple = exports.maybe = exports.Hex = exports.Buffer = exports.String = exports.Boolean = exports.Array = exports.Number = exports.Hash256bit = exports.Hash160bit = exports.Buffer256bit = exports.Network = exports.ECPoint = exports.Satoshi = exports.Signer = exports.BIP32Path = exports.UInt31 = exports.isXOnlyPoint = exports.isPoint = exports.typeforce = void 0;
const buffer_1 = require('buffer');
exports.typeforce = require('typeforce');
const ZERO32 = buffer_1.Buffer.alloc(32, 0);
const EC_P = buffer_1.Buffer.from(
'fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f',
'hex',
const EC_P = BigInt(
`0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f`,
);
const EC_B = BigInt(7);
// Idea from noble-secp256k1, to be nice to bad JS parsers
const _0n = BigInt(0);
const _1n = BigInt(1);
const _2n = BigInt(2);
const _3n = BigInt(3);
const _4n = BigInt(4);
const _5n = BigInt(5);
const _8n = BigInt(8);
function weistrass(x) {
const x2 = (x * x) % EC_P;
const x3 = (x2 * x) % EC_P;
return (x3 /* + a=0 a*x */ + EC_B) % EC_P;
}
// For prime P, the Jacobi symbol is 1 iff a is a quadratic residue mod P
function jacobiSymbol(a) {
let p = EC_P;
let sign = 1;
while (a > _1n) {
if (_0n === a % _2n) {
if (_3n === p % _8n || _5n === p % _8n) sign = -sign;
a >>= _1n;
} else {
if (_3n === p % _4n && _3n === a % _4n) sign = -sign;
[a, p] = [p % a, a];
}
}
return a === _0n ? 0 : sign > 0 ? 1 : -1;
}
function isPoint(p) {
if (!buffer_1.Buffer.isBuffer(p)) return false;
if (p.length < 33) return false;
const t = p[0];
const x = p.slice(1, 33);
if (x.compare(ZERO32) === 0) return false;
if (x.compare(EC_P) >= 0) return false;
if ((t === 0x02 || t === 0x03) && p.length === 33) {
return true;
if (p.length === 33) {
return (t === 0x02 || t === 0x03) && isXOnlyPoint(p.slice(1));
}
const y = p.slice(33);
if (y.compare(ZERO32) === 0) return false;
if (y.compare(EC_P) >= 0) return false;
if (t === 0x04 && p.length === 65) return true;
return false;
if (t !== 0x04 || p.length !== 65) return false;
const x = BigInt(`0x${p.slice(1, 33).toString('hex')}`);
if (x === _0n) return false;
if (x >= EC_P) return false;
const y = BigInt(`0x${p.slice(33).toString('hex')}`);
if (y === _0n) return false;
if (y >= EC_P) return false;
const left = (y * y) % EC_P;
const right = weistrass(x);
return (left - right) % EC_P === _0n;
}
exports.isPoint = isPoint;
function isXOnlyPoint(p) {
if (!buffer_1.Buffer.isBuffer(p)) return false;
if (p.length !== 32) return false;
const x = BigInt(`0x${p.toString('hex')}`);
if (x === _0n) return false;
if (x >= EC_P) return false;
const y2 = weistrass(x);
return jacobiSymbol(y2) === 1;
}
exports.isXOnlyPoint = isXOnlyPoint;
const UINT31_MAX = Math.pow(2, 31) - 1;
function UInt31(value) {
return exports.typeforce.UInt32(value) && value <= UINT31_MAX;
Expand Down
11 changes: 7 additions & 4 deletions ts_src/payments/p2tr.ts
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Original file line number Diff line number Diff line change
@@ -1,7 +1,11 @@
import { Buffer as NBuffer } from 'buffer';
import { bitcoin as BITCOIN_NETWORK } from '../networks';
import * as bscript from '../script';
import { typeforce as typef, TinySecp256k1Interface } from '../types';
import {
isXOnlyPoint,
typeforce as typef,
TinySecp256k1Interface,
} from '../types';
import {
toHashTree,
rootHashFromPath,
Expand Down Expand Up @@ -215,8 +219,7 @@ export function p2tr(a: Payment, opts?: PaymentOpts): Payment {
}

if (pubkey && pubkey.length) {
if (!_ecc().isXOnlyPoint(pubkey))
throw new TypeError('Invalid pubkey for p2tr');
if (!isXOnlyPoint(pubkey)) throw new TypeError('Invalid pubkey for p2tr');
}

if (a.hash && a.scriptTree) {
Expand Down Expand Up @@ -280,7 +283,7 @@ export function p2tr(a: Payment, opts?: PaymentOpts): Payment {
if (a.internalPubkey && !a.internalPubkey.equals(internalPubkey))
throw new TypeError('Internal pubkey mismatch');

if (!_ecc().isXOnlyPoint(internalPubkey))
if (!isXOnlyPoint(internalPubkey))
throw new TypeError('Invalid internalPubkey for p2tr witness');

const leafVersion = controlBlock[0] & LEAF_VERSION_MASK;
Expand Down
32 changes: 0 additions & 32 deletions ts_src/payments/verifyecc.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,38 +3,6 @@ import { TinySecp256k1Interface } from '../types';
const h = (hex: string): Buffer => Buffer.from(hex, 'hex');

export function verifyEcc(ecc: TinySecp256k1Interface): void {
assert(typeof ecc.isXOnlyPoint === 'function');
assert(
ecc.isXOnlyPoint(
h('79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798'),
),
);
assert(
ecc.isXOnlyPoint(
h('fffffffffffffffffffffffffffffffffffffffffffffffffffffffeeffffc2e'),
),
);
assert(
ecc.isXOnlyPoint(
h('f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9'),
),
);
assert(
ecc.isXOnlyPoint(
h('0000000000000000000000000000000000000000000000000000000000000001'),
),
);
assert(
!ecc.isXOnlyPoint(
h('0000000000000000000000000000000000000000000000000000000000000000'),
),
);
assert(
!ecc.isXOnlyPoint(
h('fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f'),
),
);

assert(typeof ecc.xOnlyPointAddTweak === 'function');
tweakAddVectors.forEach(t => {
const r = ecc.xOnlyPointAddTweak(h(t.pubkey), h(t.tweak));
Expand Down
73 changes: 58 additions & 15 deletions ts_src/types.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,29 +2,73 @@ import { Buffer as NBuffer } from 'buffer';

export const typeforce = require('typeforce');

const ZERO32 = NBuffer.alloc(32, 0);
const EC_P = NBuffer.from(
'fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f',
'hex',
const EC_P = BigInt(
`0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f`,
);
const EC_B = BigInt(7);
// Idea from noble-secp256k1, to be nice to bad JS parsers
const _0n = BigInt(0);
const _1n = BigInt(1);
const _2n = BigInt(2);
const _3n = BigInt(3);
const _4n = BigInt(4);
const _5n = BigInt(5);
const _8n = BigInt(8);

function weistrass(x: bigint): bigint {
const x2 = (x * x) % EC_P;
const x3 = (x2 * x) % EC_P;
return (x3 /* + a=0 a*x */ + EC_B) % EC_P;
}

// For prime P, the Jacobi symbol is 1 iff a is a quadratic residue mod P
function jacobiSymbol(a: bigint): -1 | 0 | 1 {
let p = EC_P;
let sign = 1;
while (a > _1n) {
if (_0n === a % _2n) {
if (_3n === p % _8n || _5n === p % _8n) sign = -sign;
a >>= _1n;
} else {
if (_3n === p % _4n && _3n === a % _4n) sign = -sign;
[a, p] = [p % a, a];
}
}
return a === _0n ? 0 : sign > 0 ? 1 : -1;
}

export function isPoint(p: Buffer | number | undefined | null): boolean {
if (!NBuffer.isBuffer(p)) return false;
if (p.length < 33) return false;

const t = p[0];
const x = p.slice(1, 33);
if (x.compare(ZERO32) === 0) return false;
if (x.compare(EC_P) >= 0) return false;
if ((t === 0x02 || t === 0x03) && p.length === 33) {
return true;
if (p.length === 33) {
return (t === 0x02 || t === 0x03) && isXOnlyPoint(p.slice(1));
}

const y = p.slice(33);
if (y.compare(ZERO32) === 0) return false;
if (y.compare(EC_P) >= 0) return false;
if (t === 0x04 && p.length === 65) return true;
return false;
if (t !== 0x04 || p.length !== 65) return false;

const x = BigInt(`0x${p.slice(1, 33).toString('hex')}`);
if (x === _0n) return false;
if (x >= EC_P) return false;

const y = BigInt(`0x${p.slice(33).toString('hex')}`);
if (y === _0n) return false;
if (y >= EC_P) return false;

const left = (y * y) % EC_P;
const right = weistrass(x);
return (left - right) % EC_P === _0n;
}

export function isXOnlyPoint(p: Buffer | number | undefined | null): boolean {
if (!NBuffer.isBuffer(p)) return false;
if (p.length !== 32) return false;
const x = BigInt(`0x${p.toString('hex')}`);
if (x === _0n) return false;
if (x >= EC_P) return false;
const y2 = weistrass(x);
return jacobiSymbol(y2) === 1;
}

const UINT31_MAX: number = Math.pow(2, 31) - 1;
Expand Down Expand Up @@ -80,7 +124,6 @@ export interface Tapleaf {
export type Taptree = Array<[Tapleaf, Tapleaf] | Tapleaf>;

export interface TinySecp256k1Interface {
isXOnlyPoint(p: Uint8Array): boolean;
xOnlyPointAddTweak(
p: Uint8Array,
tweak: Uint8Array,
Expand Down

3 comments on commit 1c44f41

@junderw
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Why remove isXOnlyPoint? Why not make it optional and test it only if it's present.

@brandonblack
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@brandonblack brandonblack commented on 1c44f41 Mar 23, 2022 •
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Just code simplicity. This is really just a proposal for having an in-library curve equation check, exactly when we use it vs. a provided one if available is less interesting.

BTW, I was able to bring the difference between tiny-secp256k1 native and this algorithm down from 100% slower to < 25% slower by optimizing the algorithm.

@brandonblack
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@brandonblack brandonblack commented on 1c44f41 Mar 23, 2022 •
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Here's a more discoverable / reachable place to discuss, and with the updated code that is nearly as fast as tiny-secp native: bitcoinjs#1786

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